System for maintaining oscillations in an electric timing mechanism having an oscillatory element



' June 24, 1969 HELTERLINE JR" ET AL 3,451,210 SYSTEM FOR MAINTAINING OSCILLATIONS IN AN ELECTRIC TIMING MECHANISM HAVING AN QSCILLATORY ELEMENT Filed July 1, 1966' sheet 7 of 2 a 7 PMSE M v SN5IN6 V /d saver: v cmcu/r M Cl/PCU/ 7' 1 {-46-/ 48 FIG. 2

INVENTORS LEO .4. HELTE/FLl/VE, JP. GE/PAID R. woo-rm 8Y2 F i ATTORNEY June 24, 1969 HELTERLINEQJRN ET AL 3,451,210

SYSTEM FOR MAINTAINING OSCILLATIONS IN AN ELECTRIC TIMING MECHANISM HAVING AN OSCILLATORY ELEMENT Filed July I, 1966 A Sheet of 2 l'l- I Ju i INVENTORS 150 A. REA awn/v5, JP.

ATTORNEY United States Patent M 3,451,210 SYSTEM FOR MAINTAINING OSCILLATIONS IN AN ELECTRIC TIMING MECHANISM HAVING AN OSCILLATORY ELEMENT Leo L. Helterline, Jr., Westport, and Gerald R. Wootton, Thomaston, Conn., assignors to Benrus Corporation, a corporation of Delaware Filed July 1, 1966, Ser. No. 562,222 Int. 'Cl. G04c 13/02, 13/10 US. Cl. 58-26 23 Claims ABSTRACT OF THE DISCLOSURE An electrically driven timing mechanism comprises a cyclically oscillatory element and a source of substantially cyclic timing signals, the phase relationship between the timing signals and the movement of the oscillatory element being sensed and the operative magnitude of the driving force applied to the oscillatory element being modified in accordance with that sensing, thereby to maintain the oscillations of the element in timed relation to the timing signals.

The present invention relates to a timing system particularly, but not exclusively, adapted for use in a batterypowered watch or clock.

A basic consideration in any battery-powered timing system is that the power consumption should be low enough that the battery will not become depleted too rapidly. With body-carried timekeeping devices such as wrist watches, where overall size and weight must be minimized and where, as a result, the battery must be very small, this problem becomes quite critical.

A requirement of timekeeping devices is, of course, accuracy. An error of 20 to 30 seconds a day may be tolerated, but errors much greater than that are inadmissible in quality products. Moreover, error must be maintained within admissible limits even under adverse conditions, such as radical changes in ambient temperature, maintaining the watch in odd attitudes, or the like.

One approach to the problem of watch accuracy is to use as the timing device an electronic circuit which will oscillate at a frequency which will be maintained constant to a high degree of accuracy. Such circuits are known. They often include a crystal for maintaining the frequency of oscillation accurately at desired value. The electrical oscillations occur at frequencies so high that they cannot be used directly for the driving of the watch hands or other time indicators. For example, the electrical signals may oscillate in the kilocycle per second range, whereas mechanical operations occurring at a frequency of 1 to times per second may be needed in the mechanical drive of the watch hands. While it is possible, through appropriate known circuitry, to electrically step down the output frequency of the oscillatory circuit to a frequency which could be used for mechanical drive, the step-down circuits themselves consume an appreciable amount of power, particularly in the lower ranges of frequencies. Because of the power drain this all-electronic approach, while theoretically quite desirable, is impractical. In the present stage of technology the power consumption involved is too high for the batteries presently available for use in watches.

The oscillatory balance wheel is, of course, a known timekeeping element. Its timekeeping accuracy is, however, dependent upon the precision with which the timing balance wheel is manufactured, mounted and balanced, and it is further subject to variations with temperature, movement of the watch, and the maintaining 3,451,216 Patented June 24, 1969 of the watch in odd positions or orientations. Electric watch systems utilizing a balance wheel as the timing element are in widespread use, but their accuracy is not truly satisfactory. However, they are used because the power consumption involved in their use is within satisfactory limits.

It is the prime object of the present invention to devise a timing system which incorporates the low power consumption advantages of balance Wheel drive with the improved accuracy advantages of high precision electronic oscillatory circuits.

To this end the balance wheel, in the system of the present invention, may be considered as the primary timing element. During its operation its frequency of oscillation is periodically compared with a standard provided by the oscillatory electrical circuit, which may be considered as the supervisory timing element. The operative energization of the balance wheel is varied in accordance with that comparison, so that if the balance wheel tends to rotate faster than the standard indicates it should the driving power supplied to the balance wheel is decreased, slowing it down, while if the balance wheel tends to oscillate more slowly than it should, the driving power supplied thereto is increased, thereby causing it to speed up. This comparison is made directly between the low frequency of oscillation of the balance wheel and the high frequency of oscillation of the signal from the electrical circuit, which latter may be thousands of times more rapid than the former. The comparison is made by determining the phase relationship between a given point in the cycle of low frequency oscillation of the balance wheel and a given point in the cycle of the high frequency electrical timing signal.

In the form here specifically disclosed the driving power is applied to the balance wheel in a series of pulses which occur at the frequency of oscillation of the balance wheel or at some frequency related thereto. The magnitude of the driving power imparted to the balance wheel is conveniently controlled by varying the time duration of the driving pulses; a long pulse will tend to accelerate the balance wheel, while a short pulse will tend to permit the balance wheel to decelerate.

Each time that the balance wheel reaches a predetermined point in its cycle of oscillation a phase signal is initiated, that signal being designed to last for a predetermined period of time after initiation and then to disappear. The phase signal is operatively connected to a circuit which controls the power imparted to the balance wheel drive, the operative connection being such that that circuit can supply power only during the time that the phase signal exists. However, mere existence of the phase signal is not enough to actuate the power circuit. That power circuit is in the nature of a logic AND circuit, requiring the simultaneous existence of a pair of inputs before it has an operative output. One of those inputs is the phase signal. The other input is the high frequency timing signal from the oscillatory electric circuit, and more particularly the existence of that signal in a predetremined polarity, for example, positive. Thus the pulse of driving power imparted to the balance wheel will commence when both the phase signal exists and the high frequency timing signal is positive, and the pulse of driving power will terminate a predetermined period of time after the phase signal first exists, entirely independently of the high frequency timing signal. Thus if the phase signal becomes operative at an instant when the high frequency timing signal is still negative, the commencement of driving pulse will be delayed until the timing signal becomes positive, and the driving pulse will terminate when the phase signal terminates. Hence the duration of the driving pulse will be less than that of the 3 phase signal. n the other hand, if the phase signal becomes operative at an instant that the timing signal is positive, the driving pulse will commence immediately and will last for the same period of time as the phase signal.

From this it will be seen that if the balance wheel is oscillating too rapidly the phase signal will become operative a short period of time before the timing signal becomes positive, the duration of the driving pulse will decrease, and hence the balance wheel will slow down. On the other hand, if the balance wheel oscillates too slowly, it will render the phase signal operative while the timing signal is positive, thus ensuring a driving pulse of maximum duration and producing a speeding up of the balance wheel. As a result the high degree of accuracy of the electrical oscillatory circuit, whose signal may have a frequency on the order of kilocycles per second or even higher, is imparted to the mechanical oscillatory system defined by the balance wheel, even though that mechanical system may be oscillating at a much lower rate, such as one cycle per second. The power consumption of the oscillatory circuit together with the circuits required to produce the phase signal and to produce the driving pulse is essentially the same as the power consumption of conventional electrically energized balance wheel systems such as are in widespread use today, but an improved accuracy is achieved.

It is noteworthy that the system of the present invention inherently eliminates one of the major disadvantages of balance wheel timing where the balance wheel is mechanically connected to the clockwork gears so as to drive the hands mechanically. The timing accuracy of the balance wheel is degraded in such a system because it is not free-running, but must perform work. However, in the present system any tendency on the part of the balance wheel to slow down because of the work which it must perform is automatically and inherently sensed and compensated for.

While the description thus far has been in terms of a high frequency timing signal produced by a crystal controlled electronic circuit, it should be understood that any source of high frequency timing signals could be used. For example, an electrically driven tuning fork could be employed in and of itself to provide for high frequency timing signals, or that tuning fork could be employed to stabilize and render accurate the signal oscillations from an electronic circuit, then performing substantially the same function as does the crystal in the embodiments here specifically disclosed.

The phase Signal can likewise be produced in a variety of ways. Electromagnetic coupling to the balance wheel to provide the phase signal is highly desirable, but mechanical switch actuation by the balance wheel is another of many practical ways of accomplishing the same result. The application of driving force to the balance wheel is here disclosed as being accomplished electromagnetically, but this, too, is purely exemplary.

To the accomplishment of the above, and to such other objects as may hereinafter appear, the present invention relates to a timing system as described in this specification, taken together with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of one embodiment of the present invention;

FIG. 2 is an electrical circuit diagram of the details of a system corresponding to FIG. 1;

FIG. 3 is a diagrammatic representation of the relationships between the phase signal, the timing signal, and the balance wheel driving pulse; and

FIG. 4 is a circuit diagram illustrating an alternative system embodiment.

General description As disclosed in FIG. 1, the timing system comprises a mechanical oscillatory element generally designated A,

4 here shown as a balance wheel, which is adapted to be the primary timing element, and which may also serve to mechanically drive the time indicating means such as watch hands through known gearing and linkages. The balance wheel A carries a device 2, here shown as a permanent magnet, so that the circuit generally designated 4 can produce a signal representative of the phase of the oscillations of the balance wheel A, the circuit 4 being effective to produce such an operative signal when the balance wheel A reaches a predetermined point in its cycle of movement and to cause that phase signal to continue for a predetermined period of time thereafter, the signal then becoming inoperative. The phase signal, represented by the line 6 in FIG. 1, is fed to a phase sensing circuit generally designated 8 which has another input 10 coming from a high frequency timing signal source 12. The phase sensing circuit 8 will have an output, represented by the line 14, only when there is a predetermined relationship, later described more in detail, between the inputs 6 and 10. The balance wheel A carries an element 16, here shown as a permanent magnet, by means of which the output 14 from the phase sensing circuit 8 is enabled to impart driving power to the balance wheel A, tending to maintain the balance wheel A in its oscillatory movement.

The function of the phase sensing circuit 8 is to compare the phases of the signals 6 and 10, representative respectively of the speed of oscillation of the balance wheel A and the speed of oscillation of the signal from the timing signal source 12, and to control the energization of the balance wheel A in accordance with that comparison, to the end that the balance wheel A is speeded up when it tends to lag behind the signals from the timing signal source 12 and is caused to slow down when it tends to lead the signals from the source 12. The output signals 10 from the source 12 may oscillate at any desired frequency, preferably in the kilocycle per second range or higher; the balancewheel A will oscillate at a convenient frequency, which may be on the order of 1-5 cycles per second. Despite this great disparity in the frequencies of oscillation of the timing signal 10 and the balance wheel A, effective control of the speed of oscillation of the balance wheel A is achieved.

Timing signal source 12 FIG. 2 represents the detailed embodiment of the system of FIG. 1. The timing signal source 12, enclosed within the correspondingly numbered broken line rectangle, is an essentially conventional high gain two-stage feedback amplifier defined by transistors 16 and 18, the collectors of which are connected by resistors 20 and 22 respectively and lead 24 to power source 26'. The emitters of the transistors 16' and 18 are connected by leads 28 and 30 to ground. Resistors 32 and 34 connect the collectors of the transistors 16 and 18 respectively to their respective bases. Capacitor 36 connects the collector of transistor 16' to the base of transistor 18. Lead 38 connects the collector of transistor 18 to the base of transistor 16' and it defines the feedback connection which produces oscillation. For purposes of accuracy a crystal 40 having a highly accurate oscillation frequency characteristic is interposed in that feedback path. The oscillatory output signal from the source 12 is derived from the collector of transistor 16, and is taken oif by lead 42 connected between the capacitor 36 and the collector of transistor 16. The frequency of oscillation of the signal 10 carried by the lead 42 is preferably on the order of kilocycles per second, and is represented schematically by the sinusoidal line designated 10 in FIG. 3.

Phase signal circuit 4 The phase signal circuit 4 is shown in FIG. 2 within the correspondingly numbered broken line rectangle. The permanent magnet 2- carried by the balance wheel A is designed to swing back and forth past a stationary pole piece 44 as the balance wheel A oscillates. A coil 46 is wound on the pole piece 44, one end of the coil 46 being connected by lead 48 to ground and the other end thereof being connected by lead 50 to coupling capacitor 52 forming a part of the phase signal circuit 4. The capacitor 52 is connected by lead 54 to the base of transistor 56. The collector of transistor 56 is connented by resistor 58 and lead 60 to the power source 26. Resistor 62 and capacitor 64 are connected in series around resistor 58. The emitter of transistor 56 is connected by lead 66 and resistor 68 to ground lead 70. The base of transistor 56 is connected by resistor 72 to ground. A transistor 74 has its collector connected by resistor 76 and lead 60 to power source 26, its emitter is connected by lead 78 and resistor 68 to ground, and its base is connected by lead 80 to point 82 between the resistor 62 and the capacitor 64. The output 6 from the phase signal circuit 4 is taken from the collector of transistor 74 by lead 81, and resistor 83 is connected between lead 81 and the base of transistor 56.

The operation of the phase signal circuit is as follows: Normally transistor 74 is biased on by resistor 62, and as a result transistor 56 is off. When the permanent magnet 2 carried by the balance wheel A swings past the pole piece 44 a signal pulse is electromagnetically induced in the coil 46. This pulse passes through the capacitor 52 and biases the transistor 56 on. This turns transistor 74 off, and as a result the potential on lead 81 rises, thus producing the beginning of the phase signal 6. The transistor 56 will remain on for a time determined by the parameters of resistor 62 and capacitor 64, and during that time tran sistor 74 remains off and the potential on the lead 81 remains at a high operative value. After the time determined by the values of resistor 62 and capacitor 64 has elapsed, the transistor 56 will turn off, the transistor 74 will be turned on, and the potential on line 81 will drop. The variation in potential on line 81 constitutes the phase signal 6, and is indicated graphically on FIG. 3.

A pulse from the coil 46 will be received each time that the magnet 2 passes the pole piece 44, and hence at a frequency twice that'of the cycle of oscillation of the balance wheel A. As has been indicated, the pulse signal frequency may therefore be on the order of 2 to cycles per second. As is apparent from FIG. 3, the frequency of oscillation of the timing signal 10 is much greater. Each pulse signal 6 may therefore occur approximately every 400 milliseconds, as indicated on FIG. 3, with the duration of a given phase signal 6 being approximately 1 millisecond, it being understood that these values are given solely by way of example, and that wide variation in the actual values employed is possible.

Phase sensing circuit 8 The phase sensing circuit 8 is, in FIG. 2, enclosed within the correspondingly numbered broken line rectangle. vIt comprises transistors 84 and 86 constituting a two-stage amplifier, together with transistors 88 and 90 constituting the driving pulse control section of the phase sensing circuit 8. The collector of transistor 84 and the emitter 86 are connected by resistors 92 and 94 respectively to positive line 96. The emitter of transistor 84 is connected by lead 98 to ground, and the collector of transistor 86 is connected by resistor 100 to ground. The positive line 96 is connected to line 81. The emitter of transistor 88 is connected by resistor 102 to positive line 96. Its collector is connected by leads 104 and 106 to point 108 between resistor 100 and the collector of transistor 86. The base of transistor 90 is connected by lead 109 to lead 106. Its emitter is connected by lead 110 to ground. Its collector is connected by lead 112 to the lower end of coil 114 wound about stationary pole piece 116, the other end of the winding 114 being connected by lead 118 to positive line 96. The stationary pole piece 116 is located opposite and in operative electromagnet relation to the permanent magnet 16 carried by the balance wheel A. The base of the transistor 86 is connected by lead 119 to point 122 between the collector of transistor 84 and resistor 92. The base of transistor 84 is connected by lead 124 to the output lead 42 of the timing signal source 12.

The operation of the phase sensing circuit 8 is as follows: When proper positive bias is applied to the positive line 96, the timing signal 10 carried by the lead 42 will be amplified by the transistors 84 and 86, and the output of that amplification will be carried by leads 106 and 109 to the base of transistor 90. Under normal circumstances, with proper positive bias applied, transistor is non-conductive. However, when a positive signal is applied to its base, it will become conductive, thus permitting current to flow through the coil 114, this constituting the output pulse 14 which provides driving power to the balance wheel A. When the transistor 90 becomes conductive transistor 88 will be turned on, and this will have the effect of keeping transistor 90 on even after the positive signal from lead 106 has disappeared. Transistor 90' will thus stay on for as long as proper positive bias is applied to the positive line 96-, and for as long as it stays on the winding 114 is thereby energized and the pulse 14 of driving power will be imparted to the balance wheel A.

System operation Proper positive bias for the transistors in the phase sensing circuit A will, however, only be applied during such time as the phase signal 6 is positive. It is only when the phase signal 6 is thus operatively present that the "transistors 84 and 86 can function to amplify the timing signal 10. However, merely providing proper bias to the transistors 90 and 88 will not render them conductive; it is further necessary that the base of the transistor 90 be made positive before such a conductivity state will exist, and that positive base signal will not exist unless and until the timing signal 10 is positive.

Thus the phase sensing circuit 8 functions as a logic AND circuit, having an operative output 14 produced by the conductivity of the transistor 90 which commences only when two conditions simultaneously exist-the phase signal 6 is operative and the timing signal 10 is positive. Once an output 14 from the phase sensing circuit 8 is produced that output will continue entirely independently of the polarity of the timing signal 10 until such time as proper positive bias for the transistors 88 and 90 is removed, which event will occur when the phase signal 6 becomes inoperative.

As a result, and as may be seen from the left hand end of FIG. 3, when the beginning of the phase signal 6 coincides with the existence of positive polarity for the timing signal 10, the output pulses 14a will commence immediately and will last for as long as the phase signal 6 exists, this being determined by the parameters of resistor 62 and capacitor 64 in the phase signal circuit 4. However, as can be seen from the right hand end of FIG. 3, if the phase signal 6 should commence during the time that the timing sign-a1 10 is negative, the onset of the driving pulse 14b will be delayed until the timing signal 10 goes positive. The timing pulse 14b will, however, terminate when the phase signal 6 terminates. Hence the driving pulse 14b at the right hand end of FIG. 3 is of lesser duration than the driving pulse 14a at the left hand end of FIG. 3, the difference in duration being indicated by the shaded area 120.

The system will be so designated that the duration of the driving pulse 14 required to maintain the balance wheel A in oscillation at desired cyclical frequency will be intermediate the pulse 14a of maximum length represented at the left hand end of FIG. 3 and a minimum pulse length represented by the situation which would arise if the phase signal 6 were to start just when the timing signal 10 went negative. The pulse 14b at the right hand end of FIG. 3 might represent this normal condition of intermediate duration of driving pulse. If the balance wheel A should rotate more rapidly than desired the phase signal 6 produced thereby will occur at a time 7 somewhat in advance of that shown at 14b at the right hand end of FIG. 3, and hence the shaded area 120 will increase, reducing the operative length of the driving pulse 14 and causing the balance wheel to slow down. If the balance wheel slows down too much the phase signal 6 will occur somewhat later in time, as indicated at the left hand end of FIG. 3, the operative length of the pulse 14 will increase, and the balance wheel A will :be speeded up.

An alternative embdimem-FI G. 4

FIG. 4 discloses an alternative embodiment of the system in which the phase signal 6 is not derived electronically but rather mechanically, suitable mechanism being provided so that when the balance wheel A moves through a given position it closes the switch 126 for a predetermined period of time. The timing signal source 12, from a circuit point of view, may be the same as that shown in FIG. 2, except that it may, if desired, function to produce the signals 10 at a higher frequency than in FIG. 2. The timing signal 10 from the timing signal source 12' may, through suitable circuitry, indicated by the broken line rectangle 128, be reduced to a frequency suitable for use in the present system, which frequency is still many times higher than the frequency of oscillation of the balance wheel A. While the countdown circuitry schematically represented by the broken line rectangle 128 will represent a source of power consumption, the power used by those circuits is minimal provided that the frequencies involved remain at a high level on the order of at least kilocycles per second. The phase sensing circuit 8' in the embodiment of FIG. 4 is essentially the same as that disclosed in FIG. 2. The phase signal circuit 14' in FIG. 4 comprises a mechanically actuated switch 126 utilized to connect the positive line 96 to a source of biasing voltage of proper value for a predetermined period of time.

Thus the high frequency signal 10, which may be produced with an exceptionally high degree of accuracy and with minimal power consumption, provides the basic accuracy control for the system, providing corrections to the balance wheel A so as to maintain the latter at proper speed under all conditions of operation. All of the circuitry is characterized by minimal power consumption, the actual watch hand drive may be accomplished by conventional mechanism, and thus a practical electric watch which has an exceptionally high degree of accuracy and an exceptionally low rate of power consumption may be produced at minimal cost.

While but a limited number of embodiments have been here specifically disclosed, it will be apparent that many variations may be made therein.

We claim:

1. A timing system comprising a substantially cyclically oscillatory element, a source of substantially cyclic timing signals, means operatively connected to said element for deriving therefrom a phase signal, driving means operatively connected to said element to give driving force thereto, and control means operatively connected to said driving means, to said timing signal sourceand to said phase signal means and effective to control the operative magnitude of said driving force in accordance with the phase relationship between said timing signal and said phase signal.

2. The system of claim 1, in which said timing signals occur at a cyclic frequency many times greater than the cyclic frequency of oscillation of said element.

3. The system of claim 2, in which said driving means is effective to provide pulses of driving force active on said element, said control means being effective to vary the length of said pulses, thereby to control the operative magnitude of said driving force.

4. The system of claim 2, in which said control means compares the phase relationship of predetermined points in the cycles of said timing signal and said phase signal respectively, actuates said driving means in accordance therewith, and deactuates said driving means at a predetermined time independent of the phase of said timing signal.

5. The system of claim 2, in which said control means compares the phase relationship of predetermined points in the cycles of said timing signal and said phase signal respectively, actuates said driving means in accordance therewise, and deactuates said driving means at a pre determined time determined by said phase signal independent of the phase of said timing signal.

6. The system of claim 2, in which said phase signal comprises operatively effective and ineffective portions, said control means actuates said driving means when said phase signal is effective and said timing signal reaches a predetermined point in its cycle, and deactuates said driving means a predetermined time after said phase signal has become effective.

7. The system of claim 2, in which said phase signal comprises operatively effective and ineffective portions, said phase signal is made effective at a predetermined point in the cycle of movement of said element and remains effective for a predetermined time, after which it becomes ineffective, in which said control means actuates said driving means when said phase signal is effective and said timing means reaches a predetermined point in its cycle, and in which said control means deactuates said driving means when said phase signal becomes ineffective.

8. The system of claim 2, in which said means for deriving said phase signal comprises means for sensing the attainment by said element of a predetermined point in its cycle of movement, means for initiating a phase signal output in accordance with such sensing, and means for causing said output to continue for a predetermined time.

9. The system of claim 1, in which said driving means is effective to provide pulses of driving force active on said element, said control means being effective to vary the length of said pulses, thereby to control the operative magnitude of said driving force.

10. The system of claim 1, in which said control means compares the phase relationship of predetermined points in the cycles of said timing signal and said phase signal respectively, actuates said driving means in accordance therewith, and deactuates said driving means at a predetermined time independent of the phase of said timing signal.

11. The system of claim 1, in which said control means compares the phase relationship of predetermined points in the cycles of said timing signal and said phase signal respectively, actuates said driving means in accordance therewith, and deactuates said driving means at a predetermined time determined by said phase signal independent of the phase of said timing signal.

12. The system of claim 1, in which said phase signal comprises operatively effective and ineffective portions, said control means actuates said driving means when said phase signal is effective and said timing signal reaches a predetermined point in its cycle, and deactuates said driving means a predetermined time after said phase signal has become effective.

13. The system of claim 1, in which said phase signal comprises operatively effective and ineffective portions, said phase signal is made effective at a predetermined point in the cycle of movement of said element and remains effective for a predetermined time, after which it becomes ineffective, in which said control means actuates said driving means when said phase signal is effective and said timing means reaches a predetermined point in its cycle, and in which said control means deactuates said driving means when said phase signal becomes ineffective.

14. The system of claim 1, in which said means for deriving said phase signal comprises means for sensing the attainment by said element of a predetermined point in its cycle of movement, means for initiating a phase signal output in accordance with such sensing, and means for causing said output to continue for a predetermined time.

15. The timing system of claim 1, in which said source of timing signals comprises an electronic oscillatory circuit and in which said timing signal occurs at a cyclic frequency on the order of kilocycles per second and said signal oscillates at a cyclic frequency on the order of cycles per seconds.

16. The system of claim 15, in which said driving means is effective to provide pulses of driving force active on said element, said control means being effective to vary the length of said pulses, thereby to control the operative magnitude of said driving force.

17. The system of claim 15, in which said control means compares the phase relationship of predetermined points in the cycles of said timing signal and said phase signal respectively, actuates said driving means in accordance therewith, and deactuates said driving means at a predetermined time independent of the phase of said timing signal.

18. The system of claim 15, in which said control means compares the phase relationship of predetermined points in tne cycles of said timing signal and said phase signal respectively, actuates said driving means in accordance therewith, and deactuates said driving means at a pre determined time determined by said phase signal independent of the phase of said timing signal.

19. The system of claim 15, in which said phase signal comprises operatively effective and ineffective portions, said control means actuates said driving means when said phase signal is eifective and said timing signal reaches a predetermined point in its cycle, and deactuates said driving means a predetermined time after said phase signal has become effective.

20. The system of claim 15, in which said phase signal comprises operatively effective and ineffective portions, said phase signal is made effective at a predetermined point in the cycle of movement of said element and remains effective for a predeterminedtime, after which it becames ineffective, in which said control means actuates said driving means when said phase signal is effective and said timing means reaches a predetermined point in its cycle, and in which said control means deactuates said driving means when said phase signal becomes inefiective.

21. The system of claim 15, in which said means for deriving said phase signal comprises means for sensing the attainment by said element of a predetermined point in its cycle of movement, means for initiating a phase signal output in accordance with such sensing, and means for causing said output to continue for a predetermined time.

22. A timing system comprising a substantially cyclically oscillatory element, driving means operatively connected to said element and effective to give pulses of driving force thereto, a substantially cyclic timing signal source, and control means operatively connected between said signal source and said driving means and effective to vary the duration of said pulses of driving force produced by said driving means in accordance with the phase relationship between said signal source and the oscillations of said balance wheel.

23. The system of claim 22, in which said timing signals occur at a cyclic frequency many times greater than the cyclic frequency of oscillation of said element.

References Cited UNITED STATES PATENTS 1,928,793 10/1933 Poole 58-24 RICHARD B. WILKINSON, Primary Examiner. E. C. SIMMONS, Assistant Examiner.

US. Cl. XR 5824 

